Perforated caisson jack assembly



G. E. SUDEROW PERFORATED CAISSON JACKASSEMBLY Feb. 11, 1958 5sheets-sheet 1' Filed Sept. -2, 1953 Feb. 11, 1958 G. E. suDERowv2,822,670

PERFORATED cAIssoN JACK ASSEMBLY v BYZ/ ATTORNEYS.

Feb. 11, 1958 Y 3.. E. sUDERow 2,822,676

PERFORATED cAIssoN'JAcK ASSEMBLY Filed Sept. 2, 1953 3 Sheets-Sheet 3 or l 25 Fw 23 .f @v1 5% :Ff l\ ,16 67 El \38 I Il l f W15 21 q a HIV a4l. 34 n 11 v as l 35 w/I////f//fU///l///// Z2 It 2 N .W IIIIIIHH MWeorgQEfSfudeov,

TTORNEYS PERFORATED CAISSON `ACK ASSEMBLY George E. Suderow, New York,N. Y., assig'nor to DeLong Corporation, a corporation of DelawareApplication September 2, 1953, Serial No. 378,103

11 Claims. (Cl. (S1-46.5)

The present invention relates to an improved jack assembly for raisingor lowering a supporting leg relative to a base or platform structure.vention relates to improvements in a jack assembly of the type disclosedin the patent to Pointer 2,775,869.

An important object consists in associating with a base such as the deckof a barge or the like, and a tubular member such as a caisson, animproved jack assembly including vertically spaced upper and lowerconcentric axially disposed gripper rings of such size and diameter asto loosely embrace the tubular member. Positioned between the rings arecircumferentially disposed raising and lowering means for axiallydisplacing the rings relative to each other. Associated with the r'ingsare locking means for releasably connecting the tubular member to thebase.

A further object consists in mounting a jack assembly von the deck of abarge or the like, by circumferentially fspaced tie rods, which extendthrough the upper and lower gripper rings so as to allow the rings to bemovable relative thereto and which also operatively connect the upperVring to the barge. Each of the tie rods has connected vthereto anaxially adjustable locking or retaining member which when the barge iselevated to the desired height on the caisson, is arranged to engage thelower gripper ring so as to relieve the lifting jacks of the load.

Other objects and advantages of the invention will become apparent fromthe following description when taken in conjunction with theaccompanying claims and drawings.

Referring to the drawings in which is shown a preferred kembodiment ofthe invention:

Fig. l is a sectional view taken substantially along the line 1 1 ofFigure 3.

Fig. 2 is a detailed sectional plan view taken substantially along theline 2-2 of Figure 3.

Fig. 3 is a sectional view taken substantially along the line 3`3 ofFigure 1.

Fig. 4 is a view similar to Figure 3 but showing the parts in diierentoperating positions, and

Fig. 5 is a sectional view taken substantially along the line 5--5 ofFig. l.

Fig. 6 is a perspective view of the casing assembly.

Referring to the drawings, the improved jack assembly, which isgenerally indicated vby the numeral 10 (Fig. 6), is shown for thepurpose of illustration, associated with a base or platform structure inthe form ofthe deck 11 of the oating `drilling barge 12. The deck may beprovided with one or more vertical openings 13, through each of whichextends a tubular supporting column, such as the caisson 14 which has aplurality of circumferentially symmetrically disposed longitudinal rowsof 'uniformly spaced slots or bolt-receiving apertures 21. The jackassembly 10 comprises an upper gripper ring or annular member 15 and alower concentric ring 16 which are of such diameters as to looselyreceive and embrace the caissons 14. Each ofthe rings 15 and 16 ispreferably formed with a horizontal portion or ange 17 'and an Moreparticularly, this in? l2,822,670 Patented Feb. A11, Y195,48

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angularly disposed collar or4 vertical flange 18, that ex- Y tend inopposite directions from the rings.

Each 'of vthe collars 18 has circumferentially spaced holes 19 (Figure4), in which are mounted reciprocating locking pin's or bolts 20, whichare arranged to register and extend into the slots or apertures 21formed in the wall of the caisson 14. It will be seen that when thevpins 20 of the rings 15 or 16 extend into suchv slots 21, thecorresponding ring is firmly locked to the caisson 14 against relativemovement therebetween longitudinally of the caisson. In thisconnection,it is pointed out that although the caisson or supporting column 14 hasbeen shown as being provided with bolt-receiving apertures which extendcompletely through the wall of the supporting column, it will berealized that other meanswhich arethe full equivalent of suchaperturesmay be provided on the column for cooperation with the pins 20to prevent movement of either of the rings of the jack assemblylongitudinally of the column. Itis only essential that the interengagingsurfaces between the pins and the supporting column extend substantiallytransversely of ythe latter so that Von the irnposition of loads on thepins longitudinallyrof the column, there will be no camming actionbetween such lsurfaces that will `be effective to urge displacement ofthe' vpins transversely of the supporting column.v As shown, each of thereciprocating pins 20 is connectedto a-.piston rod 22 of a double-actionfluid pressure motor 23 so vas 'to be operated by any suitable hydraulicor air pressure means from a main source of supply through the'ilexibleinlet and exhaust tubes 24 and 2S. While each of'the rings is shownprovided with three of the locking-pins' 20, circumferentiallyspacedthereon, it will be Inaiifest that any number may be employed, soas to insure the uniform locking of the caissonj14 to the jackassemblyvdulringrthe operation of the device.

vPositioned between upper ring 15 Aandithe lower ring 16 andcircumferentially disposed, relative there-tmy are spaced liftingcylinders 26 in each of which-'is mounted a reciprocating piston 273(Figure 4) thatfis` securedto the undersideof the ange 17 of the* upperring -15sovas to raise or elevate' thesa'me. Fluid'such as oil, air orsteam is introduced under pressure, in to each of the cylinders 26beneath the pistons 2f7 ythrough Vaninlet 28 from a valve housing 29that communicates with` ythe source oflluid through a pipe 3l?. Asshown, a valve 31 is associated with cach ofthe housings 29 so as toprovide auxiliary'manually operable meansfor controlling the ilow ofthefluid underfpre'ssureto the cylinderv26. Y :The upper ends of each ofthe `cylinders 26 is connected't'o atmosphere through the outlet'32. Y j

The deck 11 adjacent each of the openings 13 is formed withcircumferentially spaced apertures vorv holes. (Figure 6) through whichextend-the -tie rods ,or tension bolts' 34. Each of the rods .34 `has anenlarged head 3 5 at the upper end'thereof and extends throughverticalaligned recesses 36 in the flanges 157 Yof the upper and lower ring, andis o f suchl a length as to project lasubstanti'al distance above theupper ring 15'. Each ofthe rods 34 intermediate its ends` has a threadedportion 37 positioned above the-lowerring 16 4and arrangedto receive apolygon-al lshaped tool receiving nut 318,` fora purpose subsequentlydescribed. The lower lend preach of the rodsV 34 is also threaded -as at39 and has,I de tacbf ably connected thereto a retaining nut 40that'engagesthe underside of the deck 11 so as to limit the,upwardmovement of the bolt (Figure 5) .l

Between the upperl ringlS and the lowerring,1j6- are positioned spacedsingle-acting retracting cylinderswfll, each having a reciprocatingpiston y42 (Fig. 5) `terminating in a bifurcated lug 43 piv'otallyconnected at 44 to a lug 45 that extends upwardly from the low-erring'16. The'uppei' en'd of each cylinder '41- is pivotally connected bya link 46 and a pin 47 to a depending lug 48 on the ring 15. Fluid fromthe main source of supply is conducted into one end of each of theretracting cylinders '41 through a pipe 49 (Fig. 5) in order to retractthe pistons 42 into the cylinders. The' other end of each cylinder isconnected to atmosphere through a pipe 50. The rings 15 and 16 may beprovided with the circumferentially spaced guide members 51, each ofwhich has an inclined face 52 positioned so as to guide the caisson 14into proper position relative to the opening 13 when the parts are beingassembled or installed.

In operation of the mechanism embodying this invention, the jackiassemblies and their associated parts are initially mounted on the deck11 about the openings 13 and secured to the barge 12 by the tie rods 34.It will be seen that the lower ring 16 of each assembly will then reston the deck about the openings 13. With a jack assembly 10 in thisposition, a caisson 14 is inserted, as by 'a crane, through theassembly, with such insertion being facilitated by the inclined faces 52of the guide members S1, and through the opening or well 13 in the barge12.

During such insertion, care is taken to align the rseveral vertical rowsof openings 21 in the caisson with the corresponding pins or bolts 20 inthe jack assembly 10. With thercaisson being held in such insertedposition as by a crane (not shown) or the like, the cylinders 26 may beoperated to lift the upper ring 15 until the upper pins 20 becomealigned horizontally with a corresponding series of apertures 21 in thecaisson. At this time the fluid motors 23 of the upper ring 15 areoperated to extend its pins into the caisson apertures, to thereby lockthe ring 15 to the caisson. The caisson will thereby be supported by thejack assembly 10 and, if desired, pressure can be relieved slowly fromthe lifting cylinders 26 so that the upper ring 15 will slowly descend,carrying the caisson 10 with it, until the pistons 27 `are completelyretracted. Thereupon, pressure fluid to the cylinders 26 can be shut otand the entire weight of the caisson will be borne by the upper ring 15and transmitted through the cylinders 26 and the lower ring 16 to thedeck 11 of the barge.

Desirably, in this final barge-supported position of the caisson, thelower end thereof does not project appreciably below the bottom of thebarge 12 so that the latter can be floated to an erection site, as bybeing towed by a tug (not shown), with a minimum of towing resistance.

At an erection site, all of the caissons of vthe barge are moveddownwardly into engagement with the marine bottom by the followingsequence of operations of each iack assembly 10. In the event that thepins 20 of the lower rings 16 are not aligned with la series ofapertures 21 in the caisson, the lifting cylinders 26 are operated toliftjthe caisson, by the pins 20 of the upper ring 15, until a series ofapertures 21 in the caisson become so aligned with the pins 20 in thelower ring 16. At such time, the motors 23 of the lower ring 16 areoperated to extend their pins 20 through the aligned apertures 21 in thecaisson 14. Thereupon, the lifting cylinders 26 are operated to lowerthe upper ring 15 slightly to transfer the load of the caisson 14fromthe upper pins 20 to the lower pins 20, so that the upper pins 20 can beWithdrawn from engagement with their corresponding apertures in thecaisson.

After such withdrawal of the upper pins, the cylinders 26 are operatedto extend their piston rods 27 and lift the upper ring 15 lsubstantiallythe full stroke of the lifting cylinders until the upper pins 20 becomealigned with a higher series of apertures 21 in the caisson 14,wherelupon the motors 23 of the upper ring 15 are operated to extendtheir pins 20 through such apertures. The cylinders 26 are continued tobe operated to raise the upper ring 15 slightly to transfer the load ofthe caisson 14 from the lower pins 20 to the upper, so that such lowerpins can be withdrawn from the caisson. Fluid pressure is then slowlyrelieved from the lifting cylinders 26 to slowly lower the upper ring15, and thereby slowly lower the caisson 14 a distance equal tosubstantially the full retracting stroke of the cylinders. Thereupon,the pins 20 of the lower ring 16 'will become realigned with a higherseries of apertures 21 in the caisson 14 andere inserted thereinto. Thelifting cylinders then continue 'to lower the caisson 14 slightly untilthe load of the latter is transferred from the upper pins 20 yto thelower pins 20 so that the upper pins 20 can be retracted or withdrawnfrom the caisson.

The foregoing cycle of operations of the jack assembly 10 is repeateduntil the caisson is in engagement with the marine bottom. At that timethe jack assembly 10 is operated in the following sequence of operationsin order to raise the barge 12 on the caisson 14. With all the pins 2t)retracted, the lifting cylinders 26 are operated to lift the upper ring1S a distance substantially equal to the full extension stroke of thecylinders 26 until the upper pins 20 become aligned with a series of4apertures 21 in the caisson. The motors 23 of the upper ring 15 arethen operated to insert their pins 20 into such apertures in the caisson14. With the lower pins 20 being withdrawn from the caisson, theretracting cylinders 41 are operatedAto pull the lower ring 16 upwardwhile fluid pressure is relieved from the lifting cylinders 26, untilthe latter cylinders are substantially -completely retracted and thelower pins 20 become realigned with a higher series of apertures 21 inthe caisson 14. Thereupon, the pins of the lower rings 16 are insertedinto such apertures to thereby support the lower ring 16 on the caisson.

The upper pins 2t) are then withdrawn from the caisson and the liftingcylinders 26 operated to raise the upper ring 15. Such raising of theupper ring 15 will move the latter into engagement with the heads 35 onthe tie rods or bolts 34 so that the latter will pull the entire barge12 upwardly with the upper ring 15, Near the end of such lifting strokeof the cylinders 26 the upper pins 20 will become realigned with ahigher series of apertures 21 in the caisson 14, and at such time areinserted into such apertures. Fluid pressure is then relieved in thelifting cylinders 26 so that the load of the barge is transferred fromthe lower pins 20 to the upper pins 20. Thereupon, the lower pins 20 canbe withdrawn from the caisson 14 and the retracting cylinders 41operated to lift the lower ring 16 in order to reecycle the jackassembly for another lifting stroke in accordance with the foregoingsequence of operations.

After the barge has been raised a predetermined or desired distance onthe caissons, it will be seen that the upper pins 20 may not necessarilybecome aligned with a series of apertures 21 in the caisson 14, becausethe last step through which the barge is lifted may not be equal to thefull stroke of the cylinders 26, so that the barge cannot be supportedon the upper pins. Furthermore, it may be desirable to shut off thesource of uid pressure to the lcylinders 26 while the barge is in suchelevated position. Accordingly, while the load of the barge is on thelower pins 20 of the jack assembly, the nuts 38 on the tie rods 34 canbe screwed downwardly until they engage with the upper surface of thelower ring 16. Thereupon, relief of the fluid pressure in the cylinders26 Vwill allow the barge to settle slightly until the load of the bargeis taken by such nuts, instead of by the headed ends 35 of the rods 34.

Of course, in the event that the pins 20 of the upper ring 15 arealigned with a series of apertures 21 in the caisson 14 when the bargeis raised to its desired height on the caisson, the upper pins 20 can beinserted into such apertures so that the load of the barge can be borneby the upper pins 20 and through the heads 35 on the bolts rather thanby the nuts 38.

When drilling operations, or the like, have been completed at such amarine site and it is desired to move the barge to another marine site,the following sequence of operations is performed to lower the bargeback down into the water and to pull up the caissons 14 out ofengagement with the marine bottom so that the barge can be towed toanother marine site'.

Assuming rst that the load of the barge is` being borne by Ythe lowerpins 20 and the nuts 38, the lifting cylinders 26 are first operated tolift the upper ring 15 until the load of the barge is taken by the heads35 of the tie rods 34. Thereupon, the nuts 38 are screwed upwardly onthe tie rods 34 so as not to interferewith normal operation of the jackassembly 10. Fluid pressure is then slowly bled from the liftingcylinders 26 to thereby lower the upper ring 15, and consequently thebarge, until the pistons 27 of the cylinders 26 are substantiallycompletely retracted and the upper pins are aligned with a lower seriesof apertures 21 in the caisson and areinserted thereinto.

Making the alternative assumption, namely, that the weight of the bargein its erected position is being borne by the upper pins 20, the lowerpins are retracted, and that thetluid pressure in the cylinders 26 isrelieved, it will be seen that the cylinders 26 by their own weight dropdownwardly to the extent permitted by the full extension of theretracting cylinders 41; Consequently, the ii'st step in the lowering ofthe barge from this assumed position will be to operate the retractingcylinders 41 until the lower pins 20 become aligned with a series ofapertures in the caisson and are thereupon inserted thereinto. Thelifting cylinders 26 are thereupon operated to lift the upper ring 15slightly and also the barge, to transfer the load of the latter from theupper to the lower pins. After such transfer has been accomplished, theupper pins 20 are withdrawn from their engagement with the caisson, anduid pressure is slowly bled from the lifting cylinders 26, to therebylower the upper ring 15 together with the barge a distance substantiallyequal to the full retraction stroke of the cylinders 26. At or near theend of such stroke, the upper pins 2,0 will become aligned with a lowerseries of apertures 21 in the caisson 14 yand are inserted thereinto.This position of the parts now corresponds to that of the parts at theend of the cycle described above with reference to the first assumptlon.

Thereafter, continued bleeding of fluid from the cylinder's 26 transfersthe load of the barge from the lower pins 20 to the upper pins 20. Thelower pins'are thereupon withdrawn from the caisson 14, and thecylinders 26 will again descend by their own weight, as governed bybleeding fluid from the retracting cylinders 41, until the lower pinsbecome realigned with a lower series' of apertures in the caisson andare inserted thereinto. Fluid pressure is then again applied to thecylinders 26 to transfer the load of the barge from the upper'pins 20'to the lower pins 20. The upper pins are thereuponwithdrawn and the huidpressure slowly relieved from the cylinders 26 to lower the bargeanother step.

The 'foregoing sequence of operations is repeated until the bargebecomes afloat. The following sequence of operations is then performedin order'to raise the caissons olf the marine bottom for towing of theentirev structure to another site of operations.

Assuming that the lower pins 20 are in engagement with the caisson 14when the barge becomes aoat, the first step will be to continue to bleedfluid from the lifting cylinders 26 until the upper pins 20 becomealigned with a lower series of apertures in the caisson 14 and areinserted thereinto. The retracting cylinders 41 are then operated tolift the lower ring slightly to transfer` its weight off of the lowerpins 20, so that they can be withdrawn from the caisson 14. Thereupon,uid pressure isf slowly relieved from the retracting cylinders 41 tolower the lower ring 16 until it rests on the deck 11 of the barge. Theupperpins 20 are then .withdrawn from the caisson 14, if need be iirsttaking the Weight of the upper ring olf the upper pins by operation ofthe lifting cylinders, and iiuid pressure slowly relieved froni'thecylinders 26 to lower the upper ring 15 until the upper pins 20 becomerealigned with aA lower series ofv` apertures` 21 in the caisson 14.The' upper pins 2'0` are their inserted into such'apertures, and thecylinders l26'cpera`td to lift the upper ring 15 and consequentlythe'caiss'on 14. Near the end of the liftingy stroke of the"eyli`nde1"s26', a lower series of apertures 21 inthe caisson 14` will becomealigned with the lower pins 20, and such pins are inserted into suchapertures. The upper pins 2'0 are then withdrawn from the caisson, whilethe lo'a'd thereon is borne by the pins of the lower ring 16, and fluidpressure bled from the cylinders 26 to-low'er the upper ring 15 inpreparation for an'other'lifting stroke, on 'which the upper pins willbe reinserted into the caisson and the lower pins withdrawn. Theforegoing sequence of operations is continued in order to lift thecaissons` 14 until their lower ends are substantially flush with thebottom of the barge. The weight ofthe caissons' then can' be borne bythe lower pins and the supp-1y of fluidipressure to the jack assembly10'shut` olf during towage of the assembly to another marine site.

It will be manifest that the size and number of gripping pins and bolts,lifting cylinders, tie rods, as well as the overall arrangement of thejack assembly may be varied to suit the particular use to which thedevice is` applied.

' Moreover, the jack may be with equal facility used to elevate or lowervarious types of bothfland and marine supports, members or columns asparticular operating conditions may require. It is to be understood thatthe for-m of the invention shown is merely illustrative and that suchchanges may be made as come within'the purview of the following claims.

I claim: A'

1. In combination with a iioating barge having spaced openings in thedeck thereof, caissons extending int'o' said openings and provided withvertically spaced apertures, a jack assembly for releasably connectingthe barge tov each of the caissons and providing means for moving thecaisson relative to the barge and for movingv thebarge rel,- ative tothe caisson, said jack assembly including axially displaceab'le upperand lower rings through which the caissons extend, said rings beingindependently movable relative to each other, means connecting. theupper ring to said barge, means for moving the upper ring andk bargerelative to the lower ring, meansfor moving the lower ring relative tothe upper ring, circumferentially spaced bolts extending upwardly fromthe deck and' loosely throu-gh said rings, means on the lower end ofeach boli: engaging the underside of the deck for limiting the upwardmovement of the bolt, means on the upper ends of the bolts for limitingthe upward movement of theupper ring, reciprocating .locking pins oneach of: the rings and arranged to engage apertures in the caissons whenmoved into registration therewith, and means for actuating said pins,each of said caissons arranged to be moved by the jack assembly into xedengagement with the marine ground, and said barge when the caissons arein engage ment with the ground being operable by the jack assembly to beraised above the water.

2. In combination with a tloating barge having spaced v openings in thedeck thereof, caissons extending into said opening-s and providedwithvertically spaced apertures, a jacky assembly for releasably connectingthe barge to each of the caissons and providing means for moving-thecaisson relative to the barge and for moving 'the' barge" relative tothe caisson, said jack assembly including axially displaceable upper andlowerrings through which the caisson extends, said rings beingindependently movable relative to each other, circumferential'ly spacedlifting cyl-- inders between said rings, pistons movable in said cyl-Vinders, each of said lifting cylinders being'mounted` on the: lower ringand having its piston connected to the upper ring, retracting cylindersbetween said 'rings and'y having pistons reciprocally mountedtherein,means connecting each' retracting cylinder to one Vo'f the rings;meanscon'i necting each retracting piston to the other; of said rings,

crcumferentiallyspaced bolts extending upwardly from the deck in thebarge and loosely through said rings, meansvorn the lower endof eachbolt engaging the underside of the deck for limiting the upward movementof the bolt, reciprocating locking pins mounted on each of the rings andarranged to engage apertures in the caissons when moved intoregistration therewith, means for supplying fluid pressure to saidcylinders to selectively actuate the same, means for selectivelyactuating said pins, each of said caissons arranged to be moved by thejack assembly into fixed engagement with the marine ground, and saidbarge when the caissons are in engagement with the ground being operableby the jack assembly to be raised above the water.

3. In combination witha floating barge as called for in claim 2 in whicheach of the bolts is provided with means arranged to engage the lowerring for transferring the load on the bolts from the lifting cylindersdirectly to the lower ring.

4. In combination with a lioating barge as called for in claim 2 inwhich each bolt is provided with an intermediate threaded portion, a nutthreaded on said portion above the lower ring and arranged to engage thesame to transfer the Weight of the load on the bolts from the liftingcylinders directly to the lower ring.

5. In apparatus for erecting an over-Water platform, the combinationcomprising: an elongated leg for supporting a platform-like body, saidleg having at least two longitudinal rows of pairs of oppositely-facingabutment surfaces spaced apart longitudinally of said leg and extendinggenerally transversely thereof, said rows being arranged symmetricallyabout said leg; jacking mechanism operable on said leg for effectingrelative movement between said leg and the body in either directionlongitudinally of said leg, said mechanism including a pair of rigidmembers surrounding said leg and movable relative thereto and to eachother longitudinally of said leg, a pair of locking elements spacedalong the length of said sup porting member in alignment with each ofsaid rows, each of said elements having a pair of oppositely-facingabutment surfaces complementary to each pair of surfaces of thecorresponding row, one of said elements of each pair being mounted onone of said rigid members and the other of said elements of each pair onthe other of said rigid members and both of said elements of each pairbeing mounted for independent linear reciprocating movement generallytransversely of said leg to project and withdraw the correspondingelement pair of surfaces into and out of overlapping relation with apair of row surfaces, when aligned therewith, in order to substantiallylock the corresponding rigid member to said leg against said relativemovement in either direction therebetween or permit said relativemovement, respectively, all of said abutment surfaces beingsubstantially planar, disposed substantially normal to the length ofsaid leg, and free of camming action effective on the imposition of aload longitudinally of said leg through a complementary pair ofoverlapped and mutually engaged abutment surfaces to urge a said elementto withdraw its surfaces from a pair of row surfaces when overlappedtherewith, and a plurality of reciprocating liuid motor meansoperatively connected to said rigid members for selectively effecting orrestraining said relative movement therebetween in either direction,said motor means being arranged symmetrically about said leg and withrespect to each of said elements and the connection of at least certainof said motor means with one of said members being disposed closelyadjacent said elements thereon with less than 90 spacing,circumferentially of said one member, between each said connection andthe nearest element in order to minimize bending stresses in said onemember; and means mounting said mechanism to a platform-like body inorder to operate the mechanism to lower said leg down 8 v i intoengagement with a marine bottom, raise the bodyy and support it at leastpartially on said leg, lower the body back down' untilit is no longersupported on said leg, and pull said Vleg up out of engagement with themarine bottom for movement of the body, together with said leg andmechanism to another erection site, said one member, when said mechanismis being operated to raise or lower the body on said leg, being lockedto the leg and the other member being unlocked therefrom, and saidmounting means being connected to said other member and arrangedsymmetrically thereabout and with respect to each element thereon, saidmounting means connections being disposed closely adjacent said othermember elements to minimize bending stresses in said other member whenthe latter is locked to the leg and supporting the weight of theplatform.

6. The structure defined in claim 5 in which each pair of surfaces of arow is defined by portions of the edges of an aperture and each pair ofsurfaces of an element is defined by portions of a locking boltreceivable in a said aperture when aligned therewith.

7. The structure defined in claim 5 including poweroperated meansconnected to each of the locking elements for selectively projecting orwithdrawing the latter.

8. The structure defined in claim 5 in which the motor means arearranged to raise the said other member relative to the said one memberby extension of said motor means when said one member is locked to andsaid other member is unlocked from the leg.

9. The structure defined in claim 5 in which the extent of the elementabutment surfaces in the direction of their movement and engageable withthe leg abutment surfaces is less than the transverse dimension of theleg in' said directions, whereby the extent of locking and unlock-j ingmovements of the elements is less than said leg transverse dimension.

10. The structure defined in claim 5 in which the means mounting themechanism includes a tension element secured to the other rigid memberand securable to the body for lifting the latter when said other rigidmember is unlocked from said leg, the one rigid member is lockedthereto, andthe motor means are operated to effect upward movement ofsaid other rigid member relative to the other, and includingrelatively-vertically-adjustable, interengageable abutment means on saidtension element and on said one rigid member to support the body on saidone rigid member independently of said motor means when the latter arerendered ineffective.

1l. The structure defined in claim 5 including an adjustabledisengageable mechanical supporting connection extending between thesaid one member and the body for supporting the latter on the legindependently of said motor means, whereby after elevation of the bodyon the leg by operation of said motor means to an elevation whereat theelement pair of surfaces on the other mem ber are not in alignment witha pair of row surfaces on the leg so that said other member cannot belocked to said leg, said mechanical connection can be engaged and thepressure in said motor means can be released.

References Cited in the tile of this patent UNITED STATES PATENTS OTHERREFERENCES Pages 44-45 of Engineering News Record of May 29, 1952.

Samuelson Mar. l1, 1952 U. S. DEPRMENT OF COMMERCE PATENT OFFICECETIFICATE OF CORRECTION Patent Noo 2,822,670 February ll, 1958 GeorgeE. Suderow It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction and thatthe said Let sers Patent should read as corrected below.

Column 8, list of references cited, after line 69, add the following:

FOREIGN PATENTS LOUQ'YA France ===Jun 25, 1952 Signed and sealed this29th Clay of April 1958.

(SEAL) Attest:

KARL AXLINE ROBERT C. WATSON Comnssioner of Patents Attesting Officer

